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Australopithecus
In Episode 3.10, Helen goes back in time to kill the first hominids in order to prevent the evolution of humans who would destroy planet Earth. Facts The genus Australopithecus is a genus of extinct hominids, made up of the gracile australopiths, and formerly also included their larger relatives, the robust australopiths (which are now given their own genus). The genus Australopithecus is closely related to the human genus Homo, and may be ancestral to it. Evolution Gracile australopiths shared several traits with modern apes and humans, and were widespread throughout Eastern and Northern Africa by a time between 3.9 and 3.0 million years ago. The earliest evidence of fundamentally bipedal hominids can be observed at the site of Laetoli in Tanzania. This site contains hominid footprints that are remarkably similar to those of modern humans and have been dated to as old as 3.7 million years. Until recently, the footprints have generally been classified as australopith because that had been the only form of pre-human known to have existed in that region at that time; however, some scholars have considered reassigning them to a yet unidentified very early species of the genus Homo. Australopithecus anamensis, Australopithecus afarensis and Australopithecus africanus are among the most famous of the extinct hominids. A. africanus used to be regarded as ancestral to the genus Homo (in particular Homo erectus). However, fossils assigned to the genus Homo have been found that are older than A. africanus. Thus, the genus Homo either split off from the genus Australopithecus at an earlier date (the latest common ancestor being A. afarensis or an even earlier form, possibly Kenyanthropus platyops), or both developed from a yet possibly unknown common ancestor independently. According to the Chimpanzee Genome Project, both human (Ardipithecus, Australopithecus and Homo) and chimpanzee (Pan troglodytes and Pan paniscus) lineages diverged from a common ancestor about 5 to 6 million years ago, if we assume a constant rate of evolution. It is theoretically more likely for evolution to happen more slowly, as opposed to more quickly, from the date suggested by a gene clock (the result of which is given as a "youngest common ancestor", i.e., the latest possible date of diversion.) However, hominids discovered more recently are somewhat older than the molecular clock would theorize. Sahelanthropus tchadensis, commonly called "Toumai" is about 7 million years old and Orrorin tugenensis lived at least 6 million years ago. Since little is known of them, they remain controversial among scientists since the molecular clock in humans has determined that humans and chimpanzees had an evolutionary split at least a million years later. One theory suggests that the human and chimpanzee lineages diverged somewhat at first, then some populations interbred around one million years after diverging. Morphology The brains of most species of Australopithecus were roughly 35% of the size of that of a modern human brain. Most species of Australopithecus were diminutive and gracile, usually standing between 1.2 to 1.4 m tall(approx. 4 to 4.5 feet). In several variations of australopith there is a considerable degree of sexual dimorphism, meaning that males are larger than females. Modern hominids do not appear to display sexual dimorphism to the same degree — particularly, modern humans display a low degree of sexual dimorphism, with males being only 15% larger than females, on average. In australopiths, however, males can be up to 50% larger than females. New research suggests that sexual dimorphism may be far less pronounced than this, but there is still much debate on the subject. Diet In a 1979 preliminary microwear study of Australopithecus fossil teeth, anthropologist Alan Walker theorized that robust australopiths were largely frugivorous. However, newer methods of studying fossils have suggested the possibility that Australopithecus was omnivorous. In 1992, trace element studies of the strontium/calcium ratios in robust australopith fossils suggested the possibility of animal consumption, as they did in 1994 using stable carbon isotopic analysis. Australopithecus mainly ate fruit, vegetables, and tubers.